ICIs selectively target the PD-1/PD-L1 pathway, however, do not selectively target the PD-1/PD-L1 signaling between tumor antigen-specific T cells and tumor cells, because immune cells expressing PD-1/PD-L1 not only exist in TME but also exist in peripheral blood and normal tissues, in addition, both PD-1 and PD-L1 are expressed on not only effector CD8+ T cells called “killer T cells”, but also a variety of immune cells including other T cell subsets, B cell subsets, and antigen-presenting cells including activated monocytes, macrophages, and dendritic cells [14,37,48,49,67]. This evidence concerns the gene PDCD1 and neoplasm.